Index: source/Plugins/SymbolFile/DWARF/DWARFDebugInfo.h
===================================================================
--- source/Plugins/SymbolFile/DWARF/DWARFDebugInfo.h
+++ source/Plugins/SymbolFile/DWARF/DWARFDebugInfo.h
@@ -18,6 +18,7 @@
 #include "SymbolFileDWARF.h"
 #include "lldb/Core/STLUtils.h"
 #include "lldb/lldb-private.h"
+#include "llvm/Support/RWMutex.h"
 
 typedef std::multimap<const char *, dw_offset_t, CStringCompareFunctionObject>
     CStringToDIEMap;
@@ -74,6 +75,9 @@
   std::unique_ptr<DWARFDebugAranges>
       m_cu_aranges_ap; // A quick address to compile unit table
 
+  std::atomic_size_t m_compile_units_size_atomic { 0 };
+  mutable llvm::sys::RWMutex m_compile_units_mutex;
+
 private:
   // All parsing needs to be done partially any managed by this class as
   // accessors are called.
Index: source/Plugins/SymbolFile/DWARF/DWARFDebugInfo.cpp
===================================================================
--- source/Plugins/SymbolFile/DWARF/DWARFDebugInfo.cpp
+++ source/Plugins/SymbolFile/DWARF/DWARFDebugInfo.cpp
@@ -40,6 +40,8 @@
 // SetDwarfData
 //----------------------------------------------------------------------
 void DWARFDebugInfo::SetDwarfData(SymbolFileDWARF *dwarf2Data) {
+  llvm::sys::ScopedWriter lock(m_compile_units_mutex);
+  m_compile_units_size_atomic = 0;
   m_dwarf2Data = dwarf2Data;
   m_compile_units.clear();
 }
@@ -96,32 +98,39 @@
 }
 
 void DWARFDebugInfo::ParseCompileUnitHeadersIfNeeded() {
-  if (m_compile_units.empty()) {
-    if (m_dwarf2Data != NULL) {
-      lldb::offset_t file_offset = 0;
-      DWARFUnitSP cu_sp;
-      while ((cu_sp = DWARFCompileUnit::Extract(m_dwarf2Data, &file_offset))) {
-        m_compile_units.push_back(cu_sp);
-
-        file_offset = cu_sp->GetNextCompileUnitFileOffset();
-      }
-    }
+  if (m_compile_units_size_atomic)
+    return;
+  if (m_dwarf2Data == NULL)
+    return;
+  llvm::sys::ScopedWriter lock(m_compile_units_mutex);
+  if (!m_compile_units.empty())
+    return;
+  lldb::offset_t file_offset = 0;
+  DWARFUnitSP cu_sp;
+  while ((cu_sp = DWARFCompileUnit::Extract(m_dwarf2Data, &file_offset))) {
+    m_compile_units.push_back(cu_sp);
+
+    file_offset = cu_sp->GetNextCompileUnitFileOffset();
   }
+  m_compile_units_size_atomic = m_compile_units.size();
 }
 
 size_t DWARFDebugInfo::GetNumCompileUnits() {
   ParseCompileUnitHeadersIfNeeded();
-  return m_compile_units.size();
+  return m_compile_units_size_atomic;
 }
 
 DWARFUnit *DWARFDebugInfo::GetCompileUnitAtIndex(uint32_t idx) {
   DWARFUnit *cu = NULL;
-  if (idx < GetNumCompileUnits())
+  if (idx < GetNumCompileUnits()) {
+    llvm::sys::ScopedReader lock(m_compile_units_mutex);
     cu = m_compile_units[idx].get();
+  }
   return cu;
 }
 
 bool DWARFDebugInfo::ContainsCompileUnit(const DWARFUnit *cu) const {
+  llvm::sys::ScopedReader lock(m_compile_units_mutex);
   // Not a verify efficient function, but it is handy for use in assertions
   // to make sure that a compile unit comes from a debug information file.
   CompileUnitColl::const_iterator end_pos = m_compile_units.end();
@@ -145,6 +154,7 @@
   uint32_t cu_idx = DW_INVALID_INDEX;
   if (cu_offset != DW_INVALID_OFFSET) {
     ParseCompileUnitHeadersIfNeeded();
+    llvm::sys::ScopedReader lock(m_compile_units_mutex);
 
     // Watch out for single compile unit executable as they are pretty common
     const size_t num_cus = m_compile_units.size();
@@ -185,6 +195,7 @@
 DWARFUnit *
 DWARFDebugInfo::GetCompileUnitContainingDIEOffset(dw_offset_t die_offset) {
   ParseCompileUnitHeadersIfNeeded();
+  llvm::sys::ScopedReader lock(m_compile_units_mutex);
 
   DWARFUnitSP cu_sp;
 
@@ -494,6 +505,7 @@
   CompileUnitColl::const_iterator pos;
   uint32_t curr_depth = 0;
   ParseCompileUnitHeadersIfNeeded();
+  llvm::sys::ScopedReader lock(m_compile_units_mutex);
   for (pos = m_compile_units.begin(); pos != m_compile_units.end(); ++pos) {
     DWARFUnit *cu = pos->get();
     DumpCallback(m_dwarf2Data, cu, NULL, 0, curr_depth, &dumpInfo);